Characteristics
Manure Manure Management Systems Series
This publication is the first of a Manure Management Systems Series. This publication will be referenced by and should be used with the other publications in this series.
MWPS-18 Section 1
Manure Characteristics
Jeff Lorimor, Associate Professor, Extension Agricultural Engineer, and Wendy Powers, Assistant Professor, Animal Science, Iowa State University, Ames, Iowa, Al Sutton, Professor, Animal Science Purdue University, West Lafayette, Indiana
CONTENTS Handling Characteristics Liquid Slurry Semi-solid Solid Sampling and Testing Manure Selecting a Testing Laboratory Obtaining a Sample Laboratory Tests On-Farm Tests Using Test Results Manure Composition Common Manure Composition Nutritional Factors Influencing Manure Composition Summary Conversions Worksheet 2 2 2 3 3 3 4
Manure is a valuable source of nutrients for crops and can improve soil productivity. Manure properties depend on several factors: animal species; diet, digestibility, protein and fiber content; and animal age, housing, environment, and stage of production. Manure is characterized in several ways. Important properties for manure collection, storage, handling and utilization include the solids content (the percent of solids per unit of liquid) and the size and makeup of manure solids (fixed and volatile solids, suspended solids, and dissolved solids). Nutrient content, primarily nitrogen, phosphorus, and potassium, is important as it affects land application rates and treatment techniques. Manure components can be characterized as organic and inorganic. To help control disease and parasites, human wastes should not be mixed with animal manures.
Handling Characteristics
The quantity, composition, and consistency of manure greatly influence livestock manure facility design. The handling characteristics of manure vary, depending primarily on the amount and type of solids present, Figure 1. The boundary between handling classifications is not fixed, but varies with specific composition. Manure can be classified, in general, based on how manure must be handled. Manure handling characteristics vary as consistency changes from liquid to solid. On one end of the spectrum is lagoon liquid with a very low solids content (less than 1%) that can be handled using conventional centrifugal pumps. Lagoon liquid can be irrigated using either big guns or center pivot irrigation systems with small nozzles. On the other end of the spectrum is solid manure that must be handled with front-end loaders and/or pitchforks. Solid manure normally has more than 20% solids. In between are the more difficult to handle manures, the ones containing from 5 to 20% solids. The moisture content of the manure is the main determining characteristic, although solids size, and the presence of bedding also can influence the equipment needed for handling, treating, and transporting . Solids generally tend to settle, but very thick manures (more than 10% solids) hinder settling, and
4 4 4 9 10 10 11 12
19 20 20 21
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may result in a more uniform manure than a settled, thinner one. Sand is another challenging solid thats sometimes used as dairy bedding. Sand requires special settling and handling procedures due to its high density and abrasiveness. Nutrient values are related to solids concentrations. In general the higher the solids concentration, the higher the nutrient concentration. Estimates are available for most manure types, but to really know what manure contains, representative samples must be analyzed. Estimates and tabular values must be used with caution. They are useful for planning purposes, but once a facility is established, the best way to determine nutrient and handling characteristics is to obtain good representative samples and have them analyzed.
Liquid
1% solids, typically from 0.1 to 0.5%. However, its not uncommon for overloaded lagoons to reach as high as 2% solids.
Slurry
Manure with 4 to 10% solids content can be handled as a slurry, but may require special pumps. Swine pit manure typically contains between 2 and 6% solids. Deep pit manure will be toward the upper end of the range, while manure in outside pits will be more liquid. Outside pits may be either concrete, steel, or earthen. When wet-dry feeders or swinging waterers are used, the animals waste less water so solids content may increase to 8 to 12%, resulting in a thicker slurry. Dairy manure with milking parlor washwater added typically is handled as slurry.
Semi-solid
Manure with up to 4% solids content can be handled as a liquid with irrigation equipment. Liquids that have had the larger solids removed, or manure with dilution water added may contain 4% or less solids. Properly designed and managed anaerobic (or aerobic) lagoon treatment systems should have less than
In the 10 to 20% solids content range, handling characteristics vary by the type of solids present. In this range, the percent solids content does not have as much effect on handling characteristics as does the type of manure and the amount of bedding present.
As Excreted
Swine
As Excreted
Poultry
As Excreted
Beef (feeders)
As Excreted
Dairy cows 0 5 10 15 20 25 30
Percent total solids (wet basis)
Liquid Slurry Semi-solid Solid
Figure 1. Relative handling characteristics of different types of manure for various species.
NOTE: As-excreted lines represent the common solids content of manure excreted from a healthy animal. Manure Characteristics 3
This range of solids can be very difficult to handle and is typical of many dairy operations. The manure is too thick to pump, and too thin to scoop. Producers with this thick slurry type of manure may have to add water to handle the manure as a liquid, and will need special pumps to agitate and move the manure. Usually, handling the manure with a front-end loader doesnt work well because the liquid runs around the bucket during forward movement. Transfer equipment, such as augers and flight elevators, is sometimes used. Mechanical scrapers or skid loaders with tires attached to the bucket also can be used for manure collection.
Solid
choose a laboratory with at least two years of experience in manure testing. After the lab receives samples how does it handle those samples? Samples should be tested immediately or should be refrigerated or treated for later testing. Is the lab certified by any quality control organizations? Having tests done by a lab that meets quality control standards can help validate results. How long does a customer typically wait before results are returned? Be sure you will be able to receive your test results when you need them. When testing manure for the first time, consider sending samples to multiple (at least three) laboratories and compare results. Samples must be identical to adequately compare laboratory test results. If results are comparable, then select the least expensive laboratory that can return results in the most timely manner. If results vary, eliminate the lab or labs that provided the results that varied most. From the labs that provided results that are closest together, select the laboratory that can return results in the most timely manner.
Obtaining a Sample
Manure, not using sand bedding, with 20% solids content (80% moisture content) or more can be handled as a solid. It can be stacked, and it can be picked up with a fork or bucket loader. To handle manure with a solids content of less than 15 to 20% as a solid, liquids need to be drained, and the manure must be dried, or bedding must be added. At 20% solids or slightly less, liquid may seep from the manure stack, so a tall stack is not feasible. Once solids content exceeds 25%, seepage should not be a problem, and tall stacks will retain their shape. Poultry layer manure and poultry litter typically will have 40% solids or more. Bedded swine or bovine manure may have a wide range of solids, but likely will be solid enough to stack easily if adequate bedding is used.
Sampling and Testing Manure
Many states require producers to have a manure nutrient management plan for their operation. Having an accurate manure analysis in addition to having soil analysis and knowing crop yields will help increase the accuracy of the plan and the likelihood of plan approval by the state.
Selecting a Testing Laboratory
Most laboratories that do soil testing and/or feed analysis also will analyze manure samples. The local Extension or NRCS office should be able to assist in locating laboratories that analyze manure. Contact the laboratories before sending samples. To determine which laboratory best meets your needs, get answers to questions such as the following: For how many years has the laboratory been performing manure analysis? If possible,
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Obtaining a representative sample from each manure storage is critical to getting accurate test results. Knowing when to sample, how to collect the sample, and how to ship the sample to the testing laboratory are all important components of getting the best representative sample. When to Sample. Manure sampling and testing is needed annually to develop a historical track record. Research has found that at the same given site with the same given genetics, diet, housing, management, etc., the moisture and nutrient characteristics of the manure do not change from year-to-year. Preferably, a manure analysis should be completed just before the manure will be applied to the land. In warmer climates of the United States, the time of year when sampling occurs is critical to obtaining the proper information on lagoon operation. For example, samples taken during the summer will normally have lower analysis values than samples taken during the winter. In this case, surface sample during colder months (e.g. February) then sample the entire structure in the summer (e.g. July). The other option would be to sample annually before manure application.
How to Collect Samples. A representative sample is critical to obtaining a reliable manure analysis. Manure nutrient composition can vary significantly within the same storage. Tables 1 and 2 show the manure composition variations at different depths for unagitated lagoons and an unagitated deep pit. Agitation of manure is one of the most critical operations to perform before taking a manure sample. Nitrogen and potassium can be adequately sampled from pits by obtaining a vertical profile sample without agitation, but phosphorus requires agitation. Agitation homogenizes the manure mixture and provides a more consistent nutrient analysis as the manure is being removed. Table 2 shows that phosphorus can vary 300% or more from top to bottom without agitation. Continuous agitation is needed, even during pump out, to ensure that the phosphorus and solids stay suspended. Do not shut off the agitator to fill a tanker or to pump to a sprinkler or towed-hose system. Additionally,
Table 1. Variations in unagitated lagoons.
agitation re-suspends settled solids and ensures that most or all of the manure will flow to the inlet of the pump or removal device. Deep-pit buildings are particularly susceptible to solids buildup if not properly agitated. Many underfloor pits were not designed for convenient, effective agitation. Slurry storage may require several hours of agitation before the manure is sufficiently mixed for pumpout. Table 3 shows that the manure sampled from a pit that had been agitated for at least four hours had relatively uniform results from the first to last sample. The practice of removing a load of manure from the pit by vacuum and then blowing the manure back into the pit usually does not provide sufficient agitation to suspend solids. Agitation of manure storage facilities releases gases that may increase odor levels and present a health hazard. Considerations should be given to weather and wind conditions, time of day, and day of the week to minimize the possibility of odors affecting neighbors while the pit is being agitated.
Case studies from one swine and one dairy single-stage lagoon. Sampling depths of 2 feet and 14 feet. Lagoon depth is 18 to 20 feet. Based on data presented in Livestock Waste: A Renewable Resource, 1980, pg. 254 to 256. Component Unit Swine 2 ft Depth Total solids (TS) Volatile solids (VS) Nitrogen (N) Ammonical Nitrogen (NH4-N) Phosphorus (P2O5) Potassium (K2O) lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal 20 10 4 3 2 5 14 ft Depth 170 85 10 6 15 8 2 ft Depth 135 90 3 3 4 6 Dairy 14 ft Depth 265 177 7 2 7 8
Table 2. Variations in samples from unagitated deep-pit swine buildings.
Variation in 174 liquid swine pits in Iowa. Pits have vertical sides. Component Nitrogen (N) Ammonical Nitrogen (NH4-N) Phosphorus (P2O5) Potassium (K2O) Unit lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal Top 36 27 18 28 Middle 35 27 21 22 Bottom 51 33 72 25 Vertical Profile 38 27 31 27
Table 3. Sample comparison from well agitated deep-pits during pumping.
Samples taken from six deep pits in Iowa. All pits were agitated for at least four hours before the first load was removed and were agitated continuously during pumping. A 75-hp pump or larger was used for agitation. Component Nitrogen (N) Ammonical Nitrogen (NH4-N) Phosphorus (P2O5) Potassium (K2O)
a
Unit lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal
Profile Samplea 48.6 34.4 49.8 31.4
First Load 56.8 38.9 40.3 25.0
Middle Load 57.8 37.9 42.2 27.9
Last Load 59.5 37.8 50.3 25.8
A representative sample of the entire pit depth. Manure Characteristics 5
Sampling Procedures
Wooden handle 1. Dip sampler below the basin or lagoon surface. 2. Pull cable to open top and collect sample. 3. Close container. 4. Dump sample into a 5-gallon bucket. 5. Repeat steps 1-4 until samples from 4 to 6 locations are taken. 6. Stir the liquid in the bucket until a uniform mixture is obtained. 7. To collect laboratory sample, continue stirring the mixture. While the mixture is still in a swirling motion, dip a cup into the mixture. 8. Follow shipping procedures in Table 4 (Steps 2-4).
Sampling Devices
Stainless steel cable threaded through conduit Approximately 10' long, 1 1/2'' metal conduit
Liquid Manure
Cable
1. Insert tube vertically until the tube hits the bottom of the storage. 2. Lift the tube just enough to allow ball to seal the end of the tube after string or cable is pulled. (See opposite page for several tube variations.) 3. Pull the tube out without releasing the slurry. 4. Dump the slurry into a 5-gallon bucket. 5. Stir the slurry until a uniform mixture is obtained. 6. To collect laboratory sample, continue stirring the mixture. While the mixture is still in a swirling motion, dip a cup into the mixture. 7. Follow shipping procedures in Table 4 (Steps 2-4).
Approximately 1 1/2'' PVC tubing, 12'' longer than maximum liquid depth
Vertical Profile
Approximately 2'' rubber ball
Solid Manure
1. Insert tube into solid manure. NOTE: Tube may be difficult to insert into solid manure with feathers. A sharp spade can be used to obtain samples with feathers. 2. Dump manure into a 5-gallon bucket. A rod may be needed to push manure out of tube. 3. Repeat the first two steps until10 to 15 locations have been sampled. 4. Mix the manure until a uniform sample is obtained. 5. Follow shipping procedures in Table 5, (Steps 3-5).
3' long metal tubing
Figure 2. Using devices to obtain samples.
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Sampler Details
Hole in conduit Cable Pull cable to open top. Release cable to allow spring to close the top before removing container from the liquid.
Liquid Manure
Spring to keep top closed
Hinges
8''- 10'' PVC tubing
Endcap
Threaded rod or bolt
3/4'' diameter (approximate)
Solid rod
Vertical Profile
Thread section of tubing (approx. 1'' long)
Alternative Design I
Sampling Procedure Let threaded rod rest on bottom of storage Turn tubing until threaded rod is secured in tubing Remove sample
Solid rod Rubber stopper
Alternative Design II
Sampling Procedure Let stopper rest on bottom of storage Push PVC tubing on to stopper Remove sample
3'' diameter metal tubing
Steel rod Clean-out dowel (old broom handle) Dowel
Solid Manure
Sharpen end of tube to allow easier penetration of solid manure
Manure Characteristics
7
In the past, agitating lagoons before pumpdown was not a common practice. The relatively large volume of lagoons and relatively clean water on the lagoon surface did not indicate a compelling need for agitation. Over the years, however, the effects of sludge buildup and nutrient accumulation have became more obvious. Sludge allowed to build up over a number of years before being removed may create a significant management problem. The sludge will displace needed treatment and storage volume if not periodically removed. Lagoons receiving significant amounts of bedding may experience high rates of sludge buildup.
Lagoons are typically difficult to agitate because of their large size, but because nutrients, particularly phosphorus, tend to concentrate in sludge, thoroughly mixing during agitation is important. Effective agitation may require two or more agitators operating simultaneously at different locations around the lagoon. Continuous agitation is needed during pumping to ensure a uniform manure mixture. Extremely large lagoons may require the use of dredging equipment similar to that used in the municipal sector. Tables 4 and 5 list procedures to use when obtaining a manure sample.
Table 4. Procedure for collecting manure samples from liquid or slurry storages.
1. Obtain liquid manure. (Listed in order of sampling preference)
a. Agitate, sample and test before land application. Mix well before collection to obtain a uniform sample. b. Without agitation, sample using a long tube to sample the vertical profile. See Figure 2. c. Take several samples during emptying. Combine samples and send to a laboratory. Use results to determine the nutrient content during next application event. Quick, on-the-farm tests for ammonium-nitrogen can help adjust application rates while emptying storage. These tests take only about 10 minutes and provide reasonable estimates of ammonium-nitrogen. d. Take without agitation and sample from the surface then follow the remaining sample procedures and send to testing laboratory. After test results are returned, use Equations 3 and 4 to determine an estimated nutrient content.
2. Fill a quart-sized plastic container with a screw-on lid approximately TWO-THIRDS FULL of the sample.
Do not use a glass container. Do not completely fill the container. Close the lid tightly.
3. Label the container and ship to laboratory. Include the name, sample number, location, and date. 4. Preserve the sample by freezing if samples can not be shipped to the laboratory immediately.
CAUTION: Agitating deep-pit liquid manure storages
Gases released from agitated liquid manure can kill people and animals in a very short time. Remove people and animals from the building if possible before agitation. Open doors, vent openings, or windows, and turn on all fans to provide adequate ventilation when agitating.
Table 5. Procedure for collecting manure samples from semi-solid and solid storages.
1. Obtain samples from 10 to 15 locations in the manure stack or on the feedlot. 2. Mix these to make a composite sample. 3. Place the sample in a gallon-size plastic bag, twist, and tie tightly. 4. Label the container and ship to laboratory. Include the name, sample number, location, and date. 5. Preserve the sample by freezing if samples can not be shipped to the laboratory immediately.
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How to Ship Samples. After obtaining a sample or samples, place the container in a plastic bag. The plastic bag will help prevent leaks. If possible, deliver the manure samples to the laboratory in person. For accurate analysis keep the samples frozen or refrigerated during shipment. If this is not possible, package the sample in a strong, insulated container, such as a styrofoam-lined cardboard box. Add ice to the container, and ship the fastest way available. Some commercial laboratories provide sample containers, mailing boxes, and shipping instructions. Contact the laboratory for complete instructions before shipping.
Laboratory Tests
In addition to determining nutrient concentration, a manure analysis also can be used to determine whether a lagoon is operating properly. A manure analysis for a lagoon should also include: pH. Electrical conductivity (EC). Chlorides (to monitor salt levels). The minimum pH level for a lagoon to operate properly is about 6.5. If the pH is below 6.5, then hydrated lime or lye should be added to the lagoon until the pH level is raised to 7.0. An electrical conductivity test for lagoons has been shown to be a good indicator of ammonium nitrogen. Use Equations 1 and 2 to estimate ammoniacal nitrogen in lagoons. Testing Frequency. Tests should be performed before each land application event, or on a yearly basis initially so a historical record can be tracked. If annual manure analyses do not vary significantly in five years, then sample manure every three years. During non-test years the average test results can be used to determine land application rates. However, many factors including broken or leaky waterers, changes in
A manure analysis for land application should provide at least the following basic information: Dry matter (DM) or moisture content. Ammonium nitrogen (NH4-N). Total nitrogen or Total Kjeldahl nitrogen (TKN). Phosphorus (P2O5). Potassium (K2O). Figure 3 shows an example of a manure test analysis.
ABC Manure Testing Laboratory, Inc.
Producer: MWPS Farms Type: Swine ANALYTICAL RESULTS
ACTUAL ANALYSIS TOTAL NUTRIENTS
Date Received: Oct. 6, 2000 Date Reported: Oct. 16, 2000
Total Moisture Total Nitrogen Ammonium-Nitrogen Phosphorus (P2O5) Potassium (K2O)
96.0% 0.59% 0.46% 0.41% 0.47%
lbs/1,000 gal 50 39 35 40
VALUE ASSESSED ON AS RECEIVED BASIS AVG. VALUE SAMPLE VALUE N-Value $0.18/lb $9.00/1,000 gal P2O5-Value $0.25/lb $8.75/1,000 gal K2O-Value $0.12/lb $4.80/1,000 gal
Figure 3. Example of manure test analysis.
Manure Characteristics 9
diets, weather differences that cause changes in cooling water demand or evaporation, and precipitation falling on outdoor pits can cause differences in nutrient concentrations. The previous analysis can be a guideline for application rates until a current analysis is available, if similar management practices have been used. Reading and interpreting laboratory analyses. Samples sent to different laboratories may return with significantly different values being reported for the same elements analyzed. Does this mean that there may be an error in one of the analyses? The answer is Not necessarily. The two laboratories may actually be reporting the same results but may be presenting the information in different ways. If, for example, manure samples from the same pit were sent to two different laboratories and one lab reported a level of 0.41% P2O5 an the other lab reported 0.18% P, a first conclusion might be that the labs disagree. Actually, these labs are reporting the same value but expressing it in a different manner. To be able to compare results, first determine whether the reports are presenting the element concentration in the elemental form or in a molecular form. If a laboratory is using the elemental form in its reports, the elemental results will be listed with an elemental extension. The molecular form will not have an extension. For example, if a laboratory is reporting the elemental form of nitrate (called nitrate-nitrogen), the report will list NO3-N. The -N on the end means the results are being presented as elemental nitrogen. Elemental P and K are reported simply as P or K. Converting back and forth between elemental and molecular forms can be accomplished by using the ratios of the molecular weights: 4.43 units NO3 equals 1.0 unit NO3-N. 1.22 units NH3 equals 1.0 unit NH3-N. 1.29 units NH4 equals 1.0 unit NH4-N. 2.29 units P2O5 equals 1.0 unit P. 3.07 units PO4 equals 1.0 unit P. 1.21 units K2O equals 1.0 unit K.
The two lab results agree with each other. A conversion table has been included a the end of this publication to assist with this type of unit conversion.
On-Farm Tests
On-farm tests can provide a practical means of monitoring approximate nutrient content of liquid manure during land application. On-farm tests should be used in conjunction with but not in place of laboratory tests. As with samples sent to laboratories, samples from well-agitated storages are desirable for the most accurate analysis using on-farm testing. The most popular on-farm testing methods are the conductivity pen and the hypochlorite reaction meter. Both testing methods measure ammonium nitrogen that is used to estimate total nitrogen. The conductivity pen measures the flow of electrons due to the cations and anions of a solution. Ammonium nitrogen generally is one of the dominant cations in manure. The local water supply and salts in the ration can affect the readings of the conductivity pen, so the pen needs to be calibrated for each individual site. The hypochlorite reaction meter is a small coffeecan sized canister with a screw-on lid. Manure slurry and a reaction agent are placed in the canister before sealing. Hypochlorite from the reaction agent oxidizes the ammonium nitrogen in the slurry to produce nitrogen gas (N2). Results are obtained by reading a pressure gauge that measures the production of nitrogen gas.
Using Test Results
In the example, the first lab is reporting the elemental phosphorus as P2O5. To convert to the molecular form (P), divide 0.41% by 2.29: 0.41% (P2O5) 2.29 =0.18% (P)
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Some knowledge of the manure analysis procedure will help make the test results more understandable. Base land application on the most current test results. Apply manure based on soil tests and crop needs. Many states have regulations dictating whether application should be based on nitrogen needs or phosphorus needs. In many cases the results of the manure analysis will not be available before land-applying the manure. In these cases, analysis results from prior pumping events can be used to anticipate the present analysis (and estimate proper application rate), and the current analysis, when available, can then be used to calculate the nutrients actually applied. If the sample was collected from the surface of an unagitated deep-pit swine building, assume the test results represent approximately 95% of the total nitrogen, and 60% of the phosphorus.
Use Equations 3 and 4 to estimate the actual nutrient content of the manure when the sample was taken from the top of an unagitated pit. Top sampling is reliable for determining nitrogen content but can result in significant inaccuracies when used for estimating phosphorus content.
potassium is found in the liquid and is highly soluble. Nitrogen is split almost evenly between the solids and liquid; therefore, nitrogen is about 50% soluble and 50% insoluble.
Feces
Urine
Manure Composition
Nutrient content, primarily nitrogen, phosphorus, and potassium, is important when calculating land application rates and determining treatment techniques. Nitrogen, phosphorus, and potassium are the major nutrients of manure. Nutrients are divided between soluble and insoluble states. Soluble nutrients are more readily available for crop usage. Insoluble nutrients may not be available for crop usage for up to a year or more. Figure 4 shows the approximate distribution of the major nutrients in the feces and urine. Soluble nutrients are found in the liquid (urine), and insoluble and some soluble nutrients are found in the solids (feces) of as-excreted manure. Typically, 80% of the phosphorus is in the settled solids of manure storages and is insoluble. As much as 80% of the
Nitrogen
Phosphorus
Potassium
Figure 4. Distribution of nutrients between feces and urine. Based on NRCS Agricultural Waste Management Field Handbook, Part 651.
Equation 1. Ammoniacal nitrogen estimation in lagoons 20 to 25 feet deep.
mho mg Estimated ammoniacal nitrogen = 0.0908 x Electical Conductivity, + 73.8 L cm
Equation 2. Ammoniacal nitrogen estimation in lagoons 8 to 12 feet deep.
(r = 0.98)
mho mg Estimated ammoniacal nitrogen 181 = 0.0937 x Electical Conductivity, cm L
(r = 0.89)
Equation 3. Estimated uniform nitrogen content for a swine pit when top samples are taken and analyzed.
This equation can be used for samples taken from vertical-sided formed storages (e.g. deep pit buildings, covered and uncovered outdoor concrete and steel structures.)
Estimated nitrogen content =
(Nitrogen Test Results) 0.95
(r = 0.91)
Equation 4. Estimated uniform phosphorus content for a swine pit when top samples are taken and analyzed.
This equation can be used for samples taken from vertical-sided formed storages (e.g. deep pit buildings, covered and uncovered outdoor concrete and steel structures.) NOTE: Calculated values can vary significantly from actual concentrations.
Estimated phosphorus content =
(Phosphorus Test Results) 0.60
(r = 0.71)
Manure Characteristics
11
Manure components also can be characterized as organic and inorganic. The secondary elements (sulfur, calcium, and magnesium) are required by crops in substantial amounts. Micronutrients including zinc, boron, iron, and copper also are needed in minute quantities.
Common Manure Composition
Use the following tables to help plan storage size and to develop initial nutrient management plans before the first time the storage is emptied. These tables also can be used for site evaluation feasibility studies to estimate land requirements for manure nutrient applications. Tables presented in this section are based on reliable research data and professional standards. Raw Excreted Manure. Raw excreted manure is the manure that is defecated directly from the animal.
Table 6 presents data for raw excreted manure that has not been treated or altered. Liquid Pit Manure. Deep pit systems located underneath buildings serve to isolate manure from the outdoor environment, which minimizes some unknowns such as rainfall addition or evaporation losses and minimizes manure volumes to be treated or land applied. Isolating the manure from rainfall/runoff typically results in manure with higher total solids, and makes the manure sensitive to management inputs. An outside covered storage also will isolate the stored manure from the outside environment. Tables 7 and 8 list characteristics for liquid manure. Uncovered, outdoor liquid pit systems (concrete, steel, and earthen) are subject to rainfall and roof and land runoff if not diverted from the storage. In humid regions such as the Midwest, the manure in an
Table 6. Daily manure production and characteristics, as-excreted.
Values are as-produced estimations and do not reflect any treatment. Values do not include bedding. The actual characteristics of manure can vary 30% from table values. Increase solids and nutrients by 4% for each 1% feed wasted above 5%.
Size Animal Dairy cattle Heifer Lactating cow Dry cow Veal Beef cattle Calf High forage High forage High energy High energy Cow Swine Nursery Grow-Finish Gestating Lactating Boar Sheep Poultry Layer Broiler Turkey Duck Horse
a
a
Total manure (lb/day) (ft3/day) (gal/day) 13 21 65 106 148 82 115 9 26 62 92 54 80 63 2.7 9.5 7.5 22.5 7.2 4.0 0.26 0.18 0.90 0.33 50 0.20 0.32 1.0 1.7 2.4 1.30 1.82 0.14 0.42 1.0 1.4 0.87 1.26 1.00 0.04 0.15 0.12 0.36 0.12 0.06 0.004 0.003 0.014 0.005 0.80 1.5 2.4 7.8 12.7 17.7 9.7 13.6 1.1 3.1 7.5 11.0 6.5 9.5 7.5 0.3 1.2 0.9 2.7 0.9 0.4 0.031 0.021 0.108 0.040 5.98
Total Water Density Solids (%) 88 88 88 88 88 88 88 96 92 92 92 92 92 88 89 89 91 90 91 75 75 74 75 73 78 65 65 65 62 62 62 62 62 63 62 62 62 62 63 62 62 62 63 62 63 65 63 63 62 63 1.4 2.3 6.8 10.0 14.0 9.5 13.3 0.32 3.40 5.8 8.5 4.2 6.2 7.70 0.27 1.0 0.69 2.25 0.66 1.10 0.065 0.047 0.225 0.089 11.00
Volatile Solids 1.2 1.9 5.8 8.5 11.9 8.1 11.3 0.14 2.88 5.2 7.6 3.9 5.7 6.00 0.22 0.80 0.59 2.03 0.59 0.91 0.049 0.034 0.171 0.053 9.35
BOD5 (lb/day) 0.20 0.33 1.0 1.60 2.24 1.20 1.70 0.22 0.58 1.05 1.50 1.0 1.50 1.40 0.09 0.30 0.23 0.75 0.23 0.10 0.015 0.010 0.066 0.012 1.40
Nutrient content (lb/day) (N) 0.05 0.08 0.23 0.58 0.82 0.36 0.50 0.04 0.14 0.41 0.61 0.38 0.54 0.31 0.02 0.08 0.05 0.18 0.05 0.04 (P2O5) 0.01 0.02 0.07 0.30 0.42 0.11 0.20 0.03 0.10 0.14 0.21 0.14 0.21 0.19 0.01 0.05 0.04 0.13 0.04 0.02 (K2O) 0.04 0.07 0.22 0.31 0.48 0.28 0.40 0.06 0.11 0.25 0.36 0.22 0.32 0.26 0.01 0.04 0.04 0.14 0.04 0.04
(lbs) 150 250 750 1,000 1,400 1,000 1,400 250 450 750 1,100 750 1,100 1,000 25 150 275 375 350 100 4 2 20 6 1,000
(lb/ft3) (lb/day) (lb/day)
0.0035 0.0027 0.0016 0.0023 0.0014 0.0011 0.0126 0.0108 0.0054 0.0046 0.0038 0.0028 0.28 0.11 0.23
Weights represent the average size of the animal the during stage of production.
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Manure Management Systems Series
outdoor, uncovered pit will have lower nutrient concentration because of the addition of rainwater, compared to manure stored under roof. In dry climates, nutrient content of the manure may be higher because of water evaporation. Manure storage volumes will also be larger in humid areas, depending on any drainage area, such as the sides of an earthen storage, that contributes to the volume. Additional water will cause total manure volume to be larger, and volatilization losses of nitrogen also may be greater, resulting in fewer nutrients per head per unit time accumulating. Lagoon. Many livestock production facilities use anaerobic lagoons, especially in the southern areas of the United States. Lagoons are similar in concept to outdoor liquid pits, but lagoons are a treatment system where very large dilution volumes are present, resulting in a high volume, high nutrient loss, and low nutrient concentration manure mass. Dilution water is added to control ammonia and salt concentrations, so bacteria can function properly. When raw manure is diluted, the amount of dilution water becomes more of a controlling factor in determining the nutrient concentration per volume than the actual manure itself. Lagoons are designed to enhance microbial digestion of organic material and volatilization of nitrogen compounds. The result is significantly reduced, annual, per-head nutrient availability from lagoons as compared to liquid pit systems.
Lagoon depth is an important factor in determining nutrient retention. Research in Missouri has shown a relationship between lagoon depth and nitrogen concentrations. Deep lagoons (20 to 25 feet) had average nitrogen levels that were approximately twice the levels of shallow lagoons (8 to 12 feet). The difference is thought to be due to different surface area-to-volume ratios that affect ammonia volatilization. Table 9 shows estimated lagoon nutrient accumulations. Lagoons receiving only milking center effluent (no manure) and precipitation falling directly on the lagoon generally remain partially aerobic and reasonably odorfree. Lagoons should be designed to store milking center effluent for six to eight months. A lagoon surface area of 50 to 60 square feet per cow and a 5-foot design depth are recommended if effluent production rates are not known. Table 10 lists common milkhouse and milking parlor effluent characteristics. Nutrient concentrations in all properly operating anaerobic lagoons are very low because of the high volume of dilution water, nutrient settling, and ammonia volatilization. Because of the natural variability and very low concentration, lagoon effluent nutrient characteristics for different animal species operations (e.g. swine, beef, dairy, and sheep) are very similar. Operation management and climatic variations have the greatest influence on lagoon effluent nutrient differences. Using an estimated nutrient concentration
Table 7. Daily swine production and characteristics for manure stored in deep-pit buildings.
Actual characteristics can vary 30%. Values listed are typical of what can be found at the time of pumping. Includes dilution and spillage water. Increase solids and nutrients by 4% for each 1% feed wasted above 5%. Total Volatile Size a Total manure Water Density Solids Solids BOD5 (lbs) (lb/day)(ft3/day)(gal/day) (%) (lb/ft3) (lb/day) (lb/day) (lb/day) 25 135 135 150 150 275 375 350 2.7 5.7 7.6 7.6 10.1 7.5 22.5 7.2 0.04 0.09 0.12 0.12 0.16 0.12 0.36 0.12 0.3 0.7 0.9 0.9 1.2 0.9 2.7 0.9 89 89 89 89 89 91 90 91 62 62 62 62 62 62 63 62 0.27 0.67 0.80 0.80 1.07 0.69 2.25 0.66 0.22 0.57 0.69 0.69 0.87 0.59 2.03 0.59 0.09 0.21 0.25 0.25 0.31 0.23 0.75 0.23 Nutrient content (lb/day) (N) (P2O5) (K2O) 0.02 0.05 0.05 0.06 0.06 0.05 0.18 0.05 0.01 0.04 0.04 0.05 0.05 0.04 0.13 0.04 0.01 0.02 0.03 0.03 0.03 0.04 0.14 0.04
Animal Nursery Wean-Finish (wet/dry feeders)b, c Wean-Finish (dry feeders)c, d Grow-Finish (wet/dry feeders)b Grow-Finish (dry feeders)d Gestating Lactating Boar
a b c
Weights represent the average size of the animal during the stage of production. Dry feeders used in conjunction with cup or swinging waterers have similar results as wet/dry feeders. Wean-Finish values calculated based on pigs spending 25% of their time in nursery and 75% of their time in grow-finish. d Using nipple waterers.
Manure Characteristics
13
Table 8. Estimated liquid pit manure characteristics.
Use only for planning purposes. These values should not be used in place of a regular manure analysis Production Manure Livestock Stages Farrowing Nursery Grow-Finish (deep pit) Grow-Finish (wet/dry feeder) Grow-Finish (earthen pit) Breeding-Gestation Farrow-Finish Farrow-Feeder Dairy Cow Dairy Heifer Dairy Calf Veal Calf Dairy Herd Beef Cows Feeder Calves Finishing Cattle Broilers Pullets Layers Tom Turkeys Hen Turkeys Ducks 11,500 1,000 3,500 2,500 3,500 7,000 37,500 2,000 10,000 54,000 25,000 6,000 3,500 73,000 30,000 13,000 25,500 83 49 130 282 232 249 21 3 21 22 13 21 126 7 25 200 96 19 11 271 72 39 89 0.63 0.35 0.89 1.79 1.67 0.45 Total N NH 3-N
(lb/yr)
Concentration K 2O Units 15 3 13 12 8 20 103 6 23 123 84 17 17 193 86 35 79 0.29 0.18 0.51 0.98 0.89 0.33 per pig space per pig space per pig space per pig space per pig space per pig space per production sow per pig sold per year per production sow per mature cow per head capacity per head capacity per head capacity per mature cow per mature cow per head capacity per head capacity per bird space per bird space per bird space per bird space per bird space per bird space Total N NH 3-N P2O5 8 14 33 50 24 12 16 16 11 6 6 5 21 6 7 8 8 13 12 37 16 20 5 12 19 42 54 22 25 24 24 18 15 14 14 22 15 16 18 18 40 35 52 40 38 15 K2O 11 22 30 40 20 24 23 23 19 19 28 24 40 22 24 24 26 29 30 33 29 32 8
P2O5 17 2 18 16 9 21
lbs/1,000 gallons of manure
11 2 14 15 10 10 72 4 13 39 18 4 9 53 25 12 24 0.13 0.07 0.58 0.54 0.56 0.24
15 25 50 75 32 25 28 28 21 31 32 27 26 31 20 27 29 63 60 57 53 60 22
108 6 22 97 42 10 9 131 58 26 55 0.40 0.21 0.81 1.35 1.06 0.36
Table 9. Estimated annual manure and nutrients from lagoon effluent (lbs per year).
Use only for planning purposes. These values should not be used in place of a regular manure analysis. Production Grow-Finish Farrow-Finish Breeding-Gestation Farrowing Dairy Cow Dairy Herd Fattening Cattle Broilers Units lbs per pig space lbs per production sow lbs per pig space lbs per sow lbs per mature cow lbs per mature cow lbs per head capacity lbs per bird space Manure Produced 8,000 64,000 11,500 16,500 91,000 138,000 44,000 130 Total N 4 36 5 8 46 70 27 0.14 NH3 4 32 4 7 41 63 24 0.13 P2O5 2 23 4 6 19 30 21 0.07 K2 O 3 29 5 8 33 50 27 0.06
of 4-2-3 pounds (N-P2O5-K2O) per 1,000 gallons will be a good representative of many lagoons. Approximately 80% to 90% of nitrogen in well-seasoned steady state anaerobic lagoons is in the ammonia form.
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Solid. Like lagoons, solid manure with or without bedding is highly variable. Table 11 lists solid manure characteristics. When bedding is used, the amount of bedding will likely affect the nutrient concentration
Table 10. Estimated dairy milking center effluent characteristics.
Use only for planning purposes. These values should not be used in place of a regular manure analysis Based on NRCS Agricultural Waste Management Field Handbook, Part 651. Milkhouse & Parlor and Holding Area (scraped & flushed) Component Volume Moisture Total solids (TS) Volatile solids (VS) Fixed solids (FS) Chemical oxygen demand (COD) Biochemical oxygen demand (BOD) Nitrogen (N) Phosphorus (P2O5) Potassium (K2O) Carbon:Nitrogen (C:N) Units cu ft per day per 1,000 lbs per animal % % wet basis lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal ratio Milkhouse 0.22 99.72 0.28 12.90 10.60 25.30 0.72 0.58 1.50 10.0 Milkhouse & Parlor 0.60 99.40 0.60 35.00 15.00 41.70 8.37 1.67 0.83 2.50 12.0 Holding Area manure excluded 1.40 99.70 0.30 18.30 6.70 1.00 0.23 0.57 10.0 Holding area manure included 1.60 98.50 1.50 99.96 24.99 7.50 0.83 3.33 7.0
Table 11. Estimated solid manure characteristics.
Use only for planning purposes. These values should not be used in place of a regular manure analysis Production Manure Livestock Stages Farrowing Nursery Grow-Finish Breeding-Gestation Feeder Pig Farrow-Finish Dairy Cow Dairy Heifer Dairy Calf Veal Calf Dairy Herd Beef Cows Feeder Calves (500 lbs) Finishing Cattle Broilers Pullets Layers Tom Turkeys Hen Turkeys Ducks 4,800 480 2,100 2,000 4,540 17,140 950 28,000 13,000 3,000 2,200 40,200 13,400 7,000 11,800 18 22 39 46 46 60 34 3 17 9 23 120 7 140 65 15 10 181 47 32 65 0.41 0.53 0.66 0.92 0.92 0.42 Total N NH3-N
(lb/yr)
Concentration K 2O Units 10 1 5 5 9 43 2 84 46 8 7 141 47 28 65 0.32 0.30 0.51 0.69 0.69 0.33 per pig space per pig space per pig space per pig space per sow space per sow space per pig sold per mature cow per head capacity per head capacity per head capacity per mature cow per mature cow per head capacity per head capacity per bird space per bird space per bird space per bird space per bird space per bird space Total N NH 3-N 14 13 16 9 10 14 14 10 10 10 9 9 7 9 11 46 48 34 40 40 17 3 5 6 5 5 6 6 2 2 2 5 2 3 3 4 12 9 12 8 8 4 P 2 O5 6 8 9 7 7 8 8 3 3 3 3 4 4 4 7 53 35 51 50 50 21 K 2O 4 4 5 5 4 5 5 6 7 5 6 7 7 8 11 36 27 26 30 30 30
P2 O 5 14 2 9 7 16 69 4 42 20 5 3 80 27 14 41 0.48 0.39 0.99 1.15 1.15 0.54
lbs/ton of manure
7 1 6 5 11 51 3 28 13 3 6 40 20 11 24 0.11 0.10 0.23 0.18 0.18 0.15
Manure Characteristics
15
of the mixture more than the manure itself does. When a lot of bedding is used, nutrient concentrations will be low. On the other hand, the total nutrient retention may be greater when more bedding is used. Total nutrient losses from bedded manure are typically less than losses from liquid systems. Some reasons for the reduced loss are that the solid bedding soaks up and holds the nutrient-rich liquids, and also the carbon typical of many bedding types increases the carbon-to-nitrogen ratio. Tables 12 and 13 list the density and waterabsorbing capabilities of common bedding materials. To estimate the amount of bedding used, weigh the bedding added to each pen per week and multiply by the number of pens and weeks between cleaning. Tables 14 and 15 list approximate bedding requirements. To estimate the total weight of bedding and manure, add the amount of manure produced per animal from Table 6 (solids and liquids) to the amount of bedding. Subtract any drained liquids (not absorbed by
the bedding). If well bedded, neglect drained liquids. Equation 5 can be used to determine the total weight of manure. To estimate the volume of manure and bedding, add the manure production volume from Table 6 to one-half of the bedding volume. Bedding volume is reduced by one-half during use. Equation 6 can be used to determine the total volume of manure. Total solids for manure plus bedding can be determined using the graph in Figure 5. Open Feedlots. Manure from open feedlots can vary widely due to climate, diet, feedlot surface, animal density, and cleaning frequency. Tables 16 and 17 list typical characteristics of beef feedlot and feedlot runoff pond manure. Milking Center Effluent. Size of parlor, management, and equipment used determine the volume of effluent from milking and cleaning operations. If cow udders are washed and disinfected, then dried with paper towels, there is very little wasted water. Floors can
Table 12. Density of bedding materials.
a. Loose bedding.
Material Straw Wood Shavings Sawdust Sand Non-legume hay Alfalfa Density (lbs per cu ft) 2.5 9 12 105 4 4 Density (lbs per cu ft) 5 20 7 8 Density (lbs per cu ft) 7 14 6 6
Table 13. Absorption properties of bedding materials.
Approximate water absorption and density of dry bedding (typically 10% moisture). Water absorption Material Wood Tanning bark Fine bark Pine Chips Sawdust Shavings Needles Hardwood chips, shavings or sawdust Shredded newspaper Corn Shredded stover Ground cobs Straw Flax Oats Wheat Hay, chopped mature Shells, hulls Cocoa Peanut, cottonseed
Values are approximate
(lbs water absorbed per lb bedding)
4.0 2.5 3.0 2.5 2.0 1.0 1.5 1.6 2.5 2.1 2.6 2.5 2.2 3.0 2.7 2.5
b. Baled bedding.
Material Straw Wood Shavings Non-legume hay Alfalfa
c. Chopped bedding.
Material Straw Newspapers Non-legume hay Alfalfa
Values are approximate
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Manure Management Systems Series
Table 14. Minimum recommended bedding requirements (lbs per day per 1,000 lb of animal weight).
Housing system Dairy Stanchion barn Freestall housing Loose housing bedding area Swine (shed lot) Poultry (floor level) 5.4 9.3 3.5 5.7 2.7 11.0 4.0 3.1 3.1 1.6 35 Long straw Chopped straw Shavings Sawdust Sand
Table 15. Bedding requirements for dairy cows.
Bedding type Green sawdust
a
Moisture content Required Bedding (lbs per cow per day) (%) 75 25 10 10 28 19 9 4
Stored, uncovered Stored, covered Dried sawdust Baled straw
a
Green sawdust should be avoided to prevent klebsiella mastitis.
Equation 5. Total weight of manure.
Equation 6. Total solid manure volume using organic bedding. Does not apply to open feedlots where substantial evaporation occurs.
Manure Bedding + = Weight Weight Weight Total
Total Manure 1 Organic Bedding + = Volume Volume 2 Volume
EXAMPLE 1. Estimating bedding needs.
Desired Total Manure Solids (2)
Determine the amount of bedding needed to raise the solids content from 6 to 15%.
35 30 25 20 15 (b) 10 5 (a) 0 0 2 4 6 8 10 12 14 16 18 (c)
Initia l Man olid otal S u re T s (1)
20% 18% 14% 10% 6%
SOLUTION:
In Figure 5, find the sloped line that corresponds to the manures initial dry matter content: 1) Locate the 6% initial manure total solids line (a). 2) Locate 15% on the desired total manure solids axis, then follow the line horizontally until the line crosses the 6% initial manure total solids line (b). 3) Then go down vertically to read the pounds of bedding to be added per 100 pounds manure. This example needs 12 pounds of bedding per 100 pounds to be added to the manure.
20 22
Pounds Bedding Added Per 100 lb Manure (3)
Figure 5. Changing manure dry matter by adding bedding.
Procedure: Find the sloped line that corresponds to the Initial Manures Dry Matter content (1). Follow the line until it meets the horizontal line that corresponds to the Desired Manure Total Solids (2). Then go down to read the pounds of bedding to be added per 100 pounds of manure (3) to reach the desired solids content. Letters ingraph are for Example 1. Manure Characteristics 17
Table 16. Estimated beef feedlot manure characteristics.
Use only for planning purposes. These values should not be used in place of a regular manure analysis Based on NRCS Agricultural Waste Management Field Handbook, Part 651. Component Manure Weight Moisture Total solids (TS) Volatile solids (VS) Fixed solids (FS) Nitrogen (N) Phosphorus (P2O5) Potassium (K2O) Carbon:Nitrogen (C:N)
a b
Units lbs per day per 1,000-lb animal % % wet basis lbs per day per 1,000-lb animal lbs per day per 1,000-lb animal lbs per day per 1,000-lb animal lbs per day per 1,000-lb animal lbs per day per 1,000-lb animal lbs per day per 1,000-lb animal ratio
Unsurfaced lota 17.50 45.00 55.00 9.60 4.80 4.80 0.21 0.14 0.03 13:1
Surfaced lotb High forage diet High energy diet 11.70 53.30 46.70 5.50 3.85 1.65 5.30 52.10 47.90 2.50 1.75 0.75
Dry climate (annual rainfall less than 15 inches); annual manure removal. Dry climate; semiannual manure removal.
be washed with relatively little water using a stiffbristle broom, or hosed down with a lot of water. Small operations tend to use less cleaning water overall, but may require more water per cow per day. Depending on the source, milking center effluent can resemble: Dilute liquid manurewhen it contains large amounts of feed, bedding, and hoof dirt. Some of the solids settle; others float. Dilute milk plant effluentduring equipment washing. The suspended milk solids do not settle easily. The residual cleaning chemicals are usually concentrated enough to affect subsequent treatment and disposal. Concentrated milk-processing effluentif milk-process effluent contains colostrum or medicated or spilled milk. This effluent tends to be very high in readily biodegradable organic material and has a high BOD. Milkprocess effluent can create serious problems in waterways if the effluent should reach them. Concentrated milk-processing effluent has the potential to create serious odor problems if it is allowed to degrade anaerobically. Milkhouse and parlor effluentcannot be disposed of into field tiles, streams, lakes or ditches. Septic tank or soil absorption systems are not recommended for milking center effluent. Milk solids do not settle well in
18 Manure Management Systems Series
Table 17. Beef feedlot runoff pond manure characteristics.
Based on NRCS Agricultural Waste Management Field Handbook, Part 651.
Component Moisture Total solids (TS) Fixed solids (FS) Chemical oxygen demand (COD) Nitrogen (N) Units % % wet basis lbs per 1,000 gal lbs per 1,000 gal lbs per 1,000 gal Runoff Pond Supernatant Sludge 99.7 0.30 7.50 17.50 11.7 1.67 1.50 7.50 82.8 17.2 645 788 645 51.7 17.5 14.2
Volatile solids (VS) lbs per 1,000 gal
Ammoniacal Nitrogen (NH3-N) lbs per 1,000 gal Phosphorus (P 2O5) Potassium (K2O) lbs per 1,000 gal lbs per 1,000 gal
septic tanks, and they can carry over into the soil absorption system, resulting in plugging of the soil to the extent that absorption stops. Clear watereffluent from final pipeline rinses and water-cooled equipment. Table 10 lists some common characteristics for milking center effluent.
Nutritional Factors Influencing Manure Composition
Diets fed, as well as the manure storage systems used, and management practices, affect the nutrient content of manure. Feed Intake. Diets vary with animal type and the stage of the livestock production cycle. For instance, protein requirements decrease, and carbohydrate forms change as an animal grows to maturity, thereby decreasing the concentration of these nutrients excreted as a percent of body weight. Similarly, increased levels of minerals fed (e.g. copper, phosphorus, sodium) increase the levels of those nutrients in the manure. Nutrient analysis of manure should be done regularly, especially when major changes in management or diet formulation occur, to determine proper land application rates. Antibiotics and feed additives (e.g. copper sulfate, rumensin, and carbadox) can reduce solids degradation in manure systems, potentially causing increased solids build up (represented as sludge in the bottom of storages). Conversely, arsenic compounds (e.g. arsonilic acid, roxarsone, and avilamycin) can stimulate anaerobic decomposition and liquidification of manure. In non-ruminants, enzymes (e.g. phytase added to the rations) and reduced phosphorus in the diet can reduce phosphorus excretion from 30 to 50%. Adding feed grade amino acids to rations can reduce nitrogen excretion in manure significantly. Although sampling and the use of tabular estimates are the most common methods of estimating manure nutrients, alternative modeling methods have been proposed to allow accounting for dietary differences and their effects on manure nutrients. One problem with using tabular values is that manure nutrient estimates sometimes exceed dietary intake of the animals. Nutrient excretion varies with animal diets and the amount of the nutrients retained in the animal bodyweight and other forms of production such as milk and eggs. Use Equation 7 to calculate raw excreted manure nutrients (when no environmental influences are considered). Most producers know the feed nutrient intake of
their an...